Ok- so I changed the air filter and I found....

[rohan]

So the other day I changed the air filter on my GTO and found that it had a K&N in there but it was pretty beat up so I went ahead and put the paper one in.  I've read an article by 1 of those magazines like car and driver or something that did a test and found the K&N s didn't help any performance out so I went ahead and tossed it out.  The very first thing I noticed was that my engine was quieter and the second thing I noticed was that it didn't rev up quite as fast and seemed to have a little less power.  BUT i did get a mile or 2 more per gallon. 

So what's the deal- I noticed a difference right away but I thought they were'nt supposed to help out even let some extra dirt in the engine.    Was I imaining it was different or did it really make some small difference?

Whats the truth?

[MX793]

Differences in power typically aren't that much between a paper filter and higher flow K&N.  However, there can be a noticeable difference in engine sound (high flow filter will result in a louder intake) and a higher flow filter could result in a snappier engine response since the motor doesn't have to work as hard to draw air through the filter.

[omicron]

Instead of throwing away the filter, you threw away the whole engine. That may explain the quieter running and loss of performance.

[S204STi]

I agree with MX, the K&N probably only benefited engine response, which gives the impression of more power.  Also, did you put an AC Delco filter in there like you're supposed to or did you put a mis-fitted Fram in there?

[rohan]

Instead of throwing away the filter, you threw away the whole engine. That may explain the quieter running and loss of performance.

In the words of Professor Farnsworth--- whaaaa?

[rohan]

I agree with MX, the K&N probably only benefited engine response, which gives the impression of more power.? Also, did you put an AC Delco filter in there like you're supposed to or did you put a mis-fitted Fram in there?

Fram bad-ACDelco good?

[S204STi]

Fram bad-ACDelco good?

AC Delco=designed specifically for your vehicle, FRAM=generic fits-all design.  Beyond that, I think FRAM's quality is suspect.  That part is just my opinion.

[rohan]

Differences in power typically aren't that much between a paper filter and higher flow K&N.? However, there can be a noticeable difference in engine sound (high flow filter will result in a louder intake) and a higher flow filter could result in a snappier engine response since the motor doesn't have to work as hard to draw air through the filter.

That's what I think happened.  Let me see if I get this-  so even though it doesn't make more power- it uses the exiting power better by letting the engine "wind up" faster?  Is that right?

[rohan]

AC Delco=designed specifically for your vehicle, FRAM=generic fits-all design.? Beyond that, I think FRAM's quality is suspect.? That part is just my opinion.

Ahhhh- I don't remember what brand- big orange box with a nice pictuer of the filter on it.

[280Z Turbo]

I have heard bad things about Fram oil filters as well. Cheap junk is all they are.

[S204STi]

Ahhhh- I don't remember what brand- big orange box with a nice pictuer of the filter on it.

Haha...either way, not AC Delco.

Don't frett over it, just get the right brand next time (say, 15k miles or so).   

[J86]

I've used nothing but fram oil filters in my cars, to no ill effects.

[GoCougs]

IMO, the sound difference is giving you the impression of a change in response and/or power.

[rohan]

IMO, the sound difference is giving you the impression of a change in response and/or power.

The old flip the air filter cover over- trick?? I dunno- it seems to take a few more moments for the tach to climb up there- painfully more moments!? But you might be right!

[traumadog]

My understanding is that it's probably a relatively small difference - oiled-cotton filters do flow slightly more than paper, though the trade-off is more microscopic dirt. 

From what I've seen, I've had maybe a half-MPG increase with the K&N's in place.  That being said, cleaning a K&N if one was in there would be cheaper than buying regular paper ones over the life of the car (if that really matters to you).

And as for the dirt issue, I still wind up changing my oil every 3k miles, which although is overkill, is cheap insurance to me.

[SaltyDog]

I think you got better gas mileage because the K/N was dirty and you replaced it with a clean filter.  Cleaning the K&N might have made even better mileage.

[S204STi]

I think you got better gas mileage because the K/N was dirty and you replaced it with a clean filter.? Cleaning the K&N might have made even better mileage.

No, it doesn't. I used to use one.

Also another reason not to use them is the oil that saturates the media gradually migrates off of the filter and onto your MAF, which will impact fuel economy and may even ruin it, which I saw frequently with Nissans, causing driveability concerns.

[Pancor]

If you feel like modifying the intake of your vehicle, do it right and relpace the entire factory airbox with a tube-and-cone system from a good company.   Changing a filter isn't going to do shit.   

[r0tor]

I have a K&N replacement filter in my RX8 and generally like it.  While any power/mileage gains are small enough that it ends up being very questionable - it only cost a few bucks more then a OEM Mazda paper filter and the intake sounds a little more aggressive and can be reused over and over.

My personal theory on the sound it not increase airflow, but a decrease in sound attenuation.  My stock filter was paper, about 2x thicker, and had more pleates  - i'd think it muffles the intake sound more then a K&N does.

[AutobahnSHO]

And as for the dirt issue, I still wind up changing my oil every 3k miles, which although is overkill, is cheap insurance to me.

The dirt won't affect the oil- it will affect the air sensors (Mass airflow like R-Inge said plus others,) and then goes into the combustion chamber.
Not good for rings and pistons.

I'm sure most of it (99.9%?) just gets blown out the exhaust, but still...